All About Batteries, Part 4: Alkaline Batteries

In this article, we focus on alkaline batteries, including their advantages, disadvantages, and chemistry.

Discharging
The following illustrations are for Duracell's MV1500 Quantum AA battery. Figures 1-3 show examples of alkaline discharge curves in the form of voltage at various loads and temperatures. Figure 4 shows the battery at two load rates and illustrates the effect on internal resistance.

Figure 1

Voltage versus service hours for several constant currents. Observe the interpolated black curve that I added.

Figure 2

Voltage versus service hours for several constant-power loads.

Figure 3

Voltage versus service hours for several temperatures with a 100mA load.

Rechargeable alkaline batteries
Rechargeable alkaline batteries are sometimes called RAM batteries. The early technology was developed by Battery Technologies Inc. and licensed to Grandcell, Rayovac, Pure Energy, and EnviroCell. Additional patents have been developed to expand on the technology. The most common sizes are AAA, 9V, AA, C, and D. These batteries are manufactured fully charged and have much better charge-holding characteristics than regular rechargeable batteries like NiMH and NiCd.

These alkaline types are specifically designed to be rechargeable, with reasonably high recharging efficiency, for up to about 20 cycles. They have been designed for low-drain, periodic use, where the depth of discharge is slow and no more than 25% on average. Deep discharging reduces the cycle life substantially.

With regard to capacity, rechargeable alkaline batteries are about two-thirds as strong as their non-rechargeable counterparts. Also, terminal voltage after recharge is somewhat lower, typically recovering only to 1.4 V or so with the best brands. Also, you should recharge these batteries only using the specific charger recommended by the manufacturer.

I haven't personally tried to recharge ordinary alkaline batteries, but I believe it is technically possible. I have heard reports that, so long as the battery hasn't been discharged too deeply, it is possible to recover up to 90% of capacity with a special type of pulse charging using the Battery Xtender.

Last but certainly not least, when it comes to the disposal of alkaline batteries, this is generally easy, but you should refer to individual manufacturers for specific instructions. In my next column, we'll look at some more tips and tricks, and we will consider another battery technology. In the meantime, I welcome any questions or comments.

We who have been in batteries for awhile have also been bit by at least one thing or another. Another well-known battery company (I won't slander them here) had a supposed AA-size battery that the comapny boasted something like 15% greater capacity than any other competitor -- sure, until you discover that it had a larger diameter that gave it 15% more volume! When a few select customers complained, the company said the datasheet clearly shows the size, but would consider marking it differently than just plain 'AA'. They never made any change. Needless to say, the production run was short lived.

Another bad experience, is with cheap-spring battery holders. I designed a project using Energizer's L91 ultimate lithium battery in a battery holder. The AA battery delivers quite a punch. In my prototype, I bought a spring battery holder from [R..io Sh..k], which had bright silvery-looking contacts and springs. In about 30 seconds or so, the plastic holder was melted and the circuit quit. Measuring the contact resistance with a good 4-wire ohm meter revealed the problem. Eleven watts dissipated on a tiny spot builds heat, and the hotter the contacts got, the higher the reisitance -- talk about thermal runaway. Since I didn't plan on using that battery holder in production anyway, it turned out OK, but I did check the production version before release.

It seems like there would be many books already out there by now. I will take a gander at what is available, and if it looks like they aren't covering the topic like I want, I would consider writing one.

No, I would not be writing it for the money. Besides, I will have already given away most of the really good stuff for free for all the EETimes readers, anyway!

I think that once Ivan has finished covering all of the various battery types, followed by his "grand comparison," this series is going to make an invaluable quick-reference guide to battery technology

I think it could be expanded and made into a book. I know I would buy it. Please Ivan, allow Max to persuade you to do it. I am sure he would happily write the foreward. Just don't expect to become rich!

I agree -- I think that once Ivan has finished covering all of the various battery types, followed by his "grand comparison," this series is going to make an invaluable quick-reference guide to battery technology.